OAKLAND — Mayor Ron Dellums formalized Thursday his request for the state to investigate the Oakland Police Department’s handling of the 2007 killing of journalist Chauncey Bailey.

City internal affairs investigators are already looking into Detective Sgt. Derwin Longmire’s handling of the Bailey case and Longmire’s relationship with the former leader of Your Black Muslim Bakery, an empowerment organization tied to the killing. Dellums wants the state to conduct what he has called a “concurrent, parallel investigation” of Longmire.

“It is imperative that an investigative agency outside the City also conduct an investigation,” Dellums wrote in a five-paragraph letter to Attorney General Jerry Brown, his predecessor as Oakland mayor.

Dellums said earlier this week he was making the request in response to stories the Chauncey Bailey Project reported over the weekend that Longmire ignored evidence linking Yusuf Bey IV to the killing. A bakery dishwasher and handyman, Devaughndre Broussard, is the only person charged in the Aug. 2, 2007, slaying.

“By initiating these joint investigative measures, we will learn the truth about what happened,” Dellums wrote.

Brown, Oakland mayor from 1998 to 2006, said earlier this week he would act if asked. He had not received the letter late Thursday and would not comment on the matter, a spokeswoman for him, Christine Gasparac, said late Thursday.

Dellums also wants what he describes as a “qualified criminal investigations consultant” to aide in the probes. His spokesman, Paul Rose, said that person has not been chosen.

When appointed, he or she “will be given the information the (police department) has already developed and will build on it from there,” Rose said.

Longmire, a 23-year veteran, has not been suspended as investigations unfold. Police administrators have refused to answer questions about the matter, including his job status. Officers under internal affairs probes are often placed on administrative leave.

During recent investigations of faulty search warrants in Oakland, officers were suspended. Why Longmire has not been suspended “is a question the other 700 people” in the department are asking, an Oakland detective with knowledge of the matter said Thursday.

The investigation of Bailey’s killing has been taken over by the Alameda County District Attorney’s Office. Investigators there are looking at evidence Longmire never documented using, including Bey IV’s cell phone records, to expand the case beyond Broussard.

It was unclear late Thursday exactly how parallel investigations by both the police internal affairs division and the attorney general’s Criminal Investigations Division will work.

State Police Chiefs Association President Jerry Dyer of Fresno said it is not uncommon for law enforcement agencies to request an independent investigation. Most commonly, internal affairs would investigate violations of administrative policy and the attorney general staff would look into criminal wrongdoing.

Former Santa Clara County Superior Court Judge LaDoris Cordell said she is skeptical a concurrent investigation will succeed. Brown appointed her to the bench in 1982 when he was governor.

“The attorney general’s (staff) is being asked to come in because it has the expertise and independence to fully evaluate the Oakland police investigation into Chauncey Bailey’s murder,” she said. “So it makes no sense to me to have the attorney general come in and look over the shoulder (of internal affairs). That’s not what the attorney general does.”